1. Field of the Invention
The present invention relates to a secondary battery, and more particularly, to a secondary battery module having a plurality of unit batteries and a barrier rib for the secondary battery module.
2. Description of the Related Art
Unlike a primary battery, the secondary battery may be recharged. Lower power batteries are used for various portable electronic devices such as cellular phones, laptop computers, and camcorders. Bulk size batteries are used as the power source for motor drive, such as in hybrid electric vehicles.
Depending on the external shape, secondary batteries may be classified into different types, for example, square and cylindrical batteries. When they are used for motor drive of the machines requiring a high power source such as the hybrid electric vehicles, the secondary batteries may form a secondary battery module of high power.
The secondary battery module is formed by serially connecting several secondary batteries (hereinafter “unit battery”), and each of the unit batteries includes an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode. The electrode assembly is inserted inside a container, and a cap assembly is assembled with the container to seal the container. The cap assembly includes terminals disposed extending from the inside to the outside of the container and are electrically connected to a positive electrode and a negative electrode, respectively.
In addition, if the unit batteries are square type batteries, the unit batteries are arranged to alternate positive and negative terminals of one unit battery projected from the upper portion of the cap assembly with the positive and negative terminals of an adjacent unit battery. Adaptors of the electric conductor are typically mounted on threaded negative and positive terminals such that they are electrically connected with each other to form the battery module.
Since the battery module connects several to tens of unit batteries to form one battery module, there is a need to efficiently emit heat generated from each unit battery. In particular, when the unit battery is used as bulk size secondary batteries for motor drive such as in electric vehicles, hybrid electric vehicles, motor scooters, and vacuum cleaners, the heat emission is of significant importance.
If the heat emission does not occur properly, the temperature of the battery module may excessively increase due to the heat generated from each unit battery, and accordingly, not only the battery module but also the machines with the battery module, can malfunction.
Accordingly, when forming the battery module, a barrier rib is disposed between unit batteries, and the space between unit batteries formed by the barrier rib is used not only for cooling unit batteries but also for preventing distortion due to heat expansion of the unit batteries.
To perform such functions, the barrier rib needs sufficient strength and structure for efficient heat emission.
However, barrier ribs in the conventional secondary battery module do not satisfy the above two conditions simultaneously so there is difficulty in forming secondary battery modules of the quality which consumers expect.
That is, if the barrier ribs ensure the sufficient strength, its manufacturing cost is increased and there is restriction in designing a passage of cooling air. Alternatively, if the barrier ribs are formed having high cooling efficiency, they tend to exhibit structural weakness.